Electric discharge device and coaxial line cavity resonator therefor



Jan. 6, 1948. MICARTHUR 2,434,115

ELECTRIC DISCHARGE DEVICE AND COAXIAL LINE CAVITY RESONATOR THEREFOR Fil'ed Nov. 26, 1945 Inventor: Elm er- D. MCATTthuT,

His Attorneg.

Patented Jan. 6, 1948 2,434,115 ELECTRIC DISCHARGE DEVICE AND co- AXIAL LINE CAVITY RESONATOR THERE- FOR Elmer D. McArthur, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application November 26, 1948, Serial No. 511,818

9 Claims. (01. 31539) My invention relates to high frequency electric 7 discharge devices and, more particularly, to space-resonant systems of the ultra high frequency type.

It is an object of my invention to provide a new and improved high frequency electric discharge device.

It is another object of my invention to provide a new and improved form of ultra high frequency electric discharge device suitable for use in connection with space-resonant cavities.

It is a further object :of my invention to provide a new and improved ultra, high frequency electric discharge device of the space-resonant type in which electrodes of the device also function as inner conductors of a coaxial cavity.

It is still another object of my invention to provide a new and improved ultra high frequency device in which electrodes thereof extending in opposite directions function as inner conductors of aligned coaxial cavities.

One of the features of my invention is the provision of a new and improved ultrahigh frequency electric discharge device of the spaceresonant type comprising a plurality of enclosed electrodes formed in part by a pair of oppositely extending cylindrical metallic members which provide, respectively, externally accessible high frequency terminals and also function as inner conductors of at least a part of a space-resonant coaxial cavity, the cavities being aligned and longitudinally spaced. A transverse metallic member, supporting a control grid between the adjacent ends of the electrodes, functions to separate the aligned cavities and to provide a smooth transit from the cavity to the elements of the discharge device. The cavities may be formed by a detachable continuous metallic cylinder conductively connected to the transverse member and include means external of the electric discharge device for controlling or adjusting the frequency of the energy Within the cavities and supplied to utilization circuits connected therewith.

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. In the drawing, the single figure diagrammatically illustrates an embodiment of my invention applied to a space-resonant system and wherein a central control device used as an electric discharge device is of the construction which may be easily inserted into a concentric transmission line:

In the single figure, my invention is illustrated as including an electric discharge device I0 comprising an elongated cylindrical anode member II, an elongated cylindrical cathode member I2, and a grid or control electrode I3 maintained in spaced relation with respect to each other by a structure to be described presently. The cylindrical anode II and the cylindrical cathode I2 extend externally of the sealed region of the discharge device in opposite directions and function as at least part of space-resonant cavities I4, l5 of the coaxial line type,

The cathode I2 is arranged to have an emissive part in the form of a fiat disk surface I6 coated with a suitable electron emitting material, such as barium and strontium carbonates. The disk I6 is of a smaller diameter than the main portion ll of the cathode structure I2 and is connected thereto by means of a transverse flange or shoulder I8 and a neck portion I9. The left-hand end of the main portion I! is of slightly reduced diameter and is sealed by means of a disk 20 of insulating material, such as glass. A pair of leads 2|, sealed Within the disk 20, extend Within the hollow cathode I2 to provide connection with a heating element or filament 22 located within the neck portion I9. The metallic portions of the cathode member I 2, preferably, are constructed of a rigid conductor, such as copper-plated iron and the glass disk 20, sealed across the end of the cathode structure, is of the type having a, coefiicient of expansion substantially equal to that of the cathode material.

The anode member II similarly is provided at its end adjacent the cathode structure with a portion 24 of reduced diameter sealed at its extreme end in a fiat plate or disk 25. Preferably, for reasons which will become more apparent later, the outer diameters of the main portions of cathode I2 and anode I I are made substantially equal, Like the cathode structure, the anode II preferably is formed of a good electrical conducting material, such as copper-plated iron. The grid I 3'is supported from a transverse metallic plate 21 and a pair of insulating cylinders 28. 29, constituted by a suitable material such as glass, are hermetically sealed, respectively, between plate 21 and the transverse portion I8 of the cathode structure and between plate 21 and the transverse portion of the anode structure. In this way, the plate 21 serves also as an externally accessible high frequency terminal for grid [3. The glass cylinders 28, 29 constituted of a material having a temperature eoefiicient of expansion substantially equal to that of the anode, cathode, and the plate 21, serve to maintain the electrodes of the discharge device in spaced relation and to define a closed region about these electrodes. This region may be evacuated to a desired degree, a getter 30 enclosed within the hollow cathode l2 and connected between one of the conductors 2| and the outer portion ll serving as means to produce a desired low gas pressure Within the evacuated region. An aperture 31 in the neck portion IQ of the cathode provides communication between the previously mentioned sealed region and.

the interior of the cathode.

An important aspect of the embodiment of my invention illustrated comprises the substantially coaxially aligned anode-cathode. construction extendin in opposite directions from the transverse member 21 which defines a boundary between the cylindrical electrodes. By virtue of this construction, the discharge device is one which may be detachably incorporated in the plurality of space-resonant cavities l4 and I5 of the coaxial line type, the cylindrical anodeand cathode serving as inner conductors of these-coaxial cavities. Since these inner. conductors have equal diameters the adjacent sections of coaxial transmission lines formed thereby have; equal impedance characteristics. To define the outer wallsor concentric conductors of the cavities, I provide apair ofv tubular metallic members 35, Sit-concentrically surrounding the anode ii and the cathode [2, respectively, and conductively connected at their adjacent ends to the transverse metal plate 21, the latter serving to define one end wall of the cavities it, Hi. The adjacent ends of metallic conductors 35, 36' are provided with transverse ring members. 31, 38. attached to their ends, as by welding, the rings or flanges 31, 38 being secured'together by means of bolts 39; The rings 31', 38, at their inner edges, are provided with a pluralityof spring-like fingers 40 which engage the outer surface of the transverse metal plate member 21.

The space-resonant system shown comprises two tuned resonant cavities or regions, one of which is the anode-grid cavity I4 and is defined by the anode II, the transverse member 21, and the outer cylinder 35and the other of which is the grid-cathode cavity. and is defined by the cylindrical cathode l2, the transverse member 21, and the-outer cylinder 36. A pair of cylindrical inner conductors 42, 43, having at their ends a plurality of spring-like fingers l -i, slide over the outer ends, respectively, of the anode II and the cathode l2 to serve as supports for maintaining the dischargedevice concentrically aligned and as extensions of the inner conductors of which these electrodes form a part. The inner conductors Q2, 53 may be maintained in concentric position within the outer conductors 35; 36" by means of any required number of insulators 45.

In connection with the space-resonant system, means are provided for tuning or controlling the natural resonant frequency of the cavities M, 15. This means may take the form of the annular plungers 46, Q1 positionable within the cylinders 35,- 36. The p-lungers 46, ll have a longitudinal lengthequal to a quarter wave length of the oscillationswithin cavities M, 5 and are in spaced relation with the inner surfaces of cylinders 35, 35 and the outer surfaces of the anode Hand cathode l2 and the hollow conductors 42, 43 connected therewith to provide a required capacitive coupling for the ultra high frequency currents of the space resonant system, these plungers being insulated from the respective electrodesandassociated-conductors for unidirectional currentsby means of this spacing. The positions of plungers 46, M may be adjusted by any suitable mechanical expedient, such as the rods 49, and energy may be extracted from the space-resonant region by any suitable output electrode means, one form oi'which may be the capacitive probe or plate 50 extending into the cavity M in spaced relation with the anode H and connected to a conductor 51 to form a part of a coaxial transmission line having anouter conductor 52 conductively connected to the outer cylinder A similar energy extracting or energy coupling means may be employed with the cathode-grid cavity, if desired.

Upon impressing a suitable unidirectional voltage across the anode Ii by means of conductor 54 and across cathode l2 by means of conductor 5.5-, high frequency electromagnetic energy may be derived from the space-resonant system through thetransmission line comprising conductors 5!, 52. From the standpoint of elementary analysis of the-operation of the-system as a whole, it may be considered that the coupling between the anode-grid and grid-cathode regions is obtained by virtue of the mutual capacitance between the opposingsurfaces of anode H and cathode l2 so that energy may be fed back from the anode-grid cavity to the grid-cathode cavity maintaining the system in a state of oscillation.

The occurrence of such oscillation depends, of course, upon the assumption that proper resonance conditions are provided by the tuning of the transmission line sections by means of the plungers LlB-and ll and that ample feed back exists between the anode and grid circuits. Under some conditions, the internal plate-to-cathode capacitance of the tube described. above is surficient to maintain such oscillations. In most cases, however, it is desirable that this coupling be augmented in some way and, to this end, there is provided in the present instance a; coupling element 51 which extends between the anode-grid andgrid cathode cavities. Since the two cavities are engaged end-on, that is, are adjacent and coaxially aligned, it is possible to obtain a smooth transit from the main part of the coaxial cavities defined by the outer conductors 35, 3b, the plungers 45, ll, the inner conductors A2, 33, and the enlarged sections of the anode and cathode to the active portions of the tube elements. All the corners or other changes of direction of the electromagnetic waves within the cavities are thus made very small. The spring fingers all engage the transverse plate 2'! which defines the adjacent ends of the cavities and provide a smooth path for current'fiow on both sides of the common wall Zlof the cavities. In this manner, the necessity of employing re-entrantsections between the active elements. of the discharge device and the space-resonant cavities connected therewith is avoided; The particular electric discharge device shownis of a structure which may be easily inserted between adjacent sections of a concentric transmission line to function as a smooth continuation of these sections, the grid of the device being. conductively connected to the outer conductor of the transmission line and the anode and cathode forming extensions of the inner conductors of the line. The construction of the system is such that the tuning plungers #55, ll may be pressed inwardly from either end until they actually overlap the glass cylinders 28, 29 and reach disk Zl. In other words, the structure of the electric discharge device is such that there is no interference with the sliding of the plungers &6, 4? over the glass cylinders to define a very 7 is ppe e v i h means-of metallic supports BI and is provided lwitlra plurality of holes 62,

hand end of the tube 69.

or; where operating conditions require, may be hollow and cooled by any cooling medium, such as air. A construction suitable for this purpose is shown in the drawing in which a hollow tube the hollow anode H by by means of which the airmay be directed against the walls of the anode in addition to the stream of-air-direct ed against the activesurface 25 from the open left- The tube 59,, at its right-hand end, may engage, through a slip con- "nection, a similar hollow tube 64 supported-within inner conductor ,42.

:Although in the above described embodiment of my invention I have chosen to represent certain of the structural features as applied to a space-resonant system used as an oscillator, it is readily apparent that the improved structure and system which I provide may be applied with equal facility to space-resonant systems used for other purposes, such as amplifiers, converters, and the like. Furthermore, while I have shown the employment of a pair of outer cylindrical conductors 35, 35, a single metal cylinder may be used instead. this cylinder being conductively connected to the platev 21 defining a wall between adjacent cavities within the cylinder.

Also, while in certain of the above descriptive matter and in the accompanying claims the term connection or connected has been used relative to certain of the members defining the ultra high frequency regions, it will be appreciated that this term has been used in the sense of permitting the transfer of energy at .ultra high frequencies and is not to be construed as being limited to a conductive connection, inasmuch as it will be apparent to those skilled in the art-that, in some instances, it may be desirable to connect certain of the parts through an inter-spaced insulating means, in which instances the high frequency energy is, of course, transmitted by virtue of the electrostatic coupling between the parts or elements.

While I have shown a particular embodiment of my invention, it willof course be understood that I do not wish to be limited thereto since various modifications may be made, and I contemplate by the appended claims to cover any such modifications as fall within the true spiritand scope ofmy invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A high frequency cavity resonator apparatus comprising an electric discharge device including cylindrical anode and cathode members of substantially equal diameter positioned incoaxial longitudinal alignment and having juxtaposed closed nds. ro ide w th axiel yq x sn s tually spaced portions of reduced diameter constituting an electron receiving surface and an electron emitting surface respectively, a transverse conductive member supporting a grid between said anodeandcath-ode members in spaced relation to said portions, insulating means positioning said anode and cathode members and said conductive member in mutually spaced relation and forming a sealed region about said ends and said portionssaid anodeinember and said cathode memberconstituting-at least a portion of a" member forming with transverse conductive continuous inner conductor of a concentric line conductor for said concentric line, said transverse conductive member being conductively attached to said cylindrical conductive member, said cylindricalv conductive member forming with said anode and cathode members at least portions of a pair of cavity resonators one on each side of said grid.

2. Apparatus as in claim 1 including adjustable plunger means between said cylindrical conductive member and said anode and oath-ode members for tuning said cavity resonators.

3. A high frequency cavity resonator apparatus comprising an electric discharge device'ineluding cylindrical anode and cathode members of equal diameter positioned in coaxial longitudinal alignment and having juxtaposed closed ends provided with an electron receiving surface and an electron emitting surface respectively, a transverse conductive member supporting a grid between said anode and cathode members in spaced relation to said ends, insulating means positioning said anode and cathode members and said conductive member in mutually spaced relation and forming a sealed region about said ends, said anode member and said cathode member constituting at least a portion of a continuous inner conductor-of a concentric line interrupted only by said sealed region, and a cylindrical conductive member concentrically surrounding said device and constituting an outer conductor for said con-' centric line, said transverse conductive member being conductively attached to said cylindrical conductive member, said cylindrical conductive said anode and cathode membersat least portions of a pair of cavity resonators one on each side of said grid.

4. A high frequency cavity resonator apparatus comprising an electric discharge device including cylindrical anode and cathode members of equal diameter positioned in coaxial longitudinal alignment and having juxtaposed closed ends provided with an electron receiving surface and an electron emitting surface respectively, a member supporting a grid between said anode and cathode members in spaced relation to said ends, insulating cylinders of diameter equal to that of said anode and cathode members coaxially aligned therewith and positioning said anode and cathode members and said conductive member in mutually spaced relation and forming a sealed region aboutsaid ends, said anode member and said cathode member constituting at least a portion of a continuous inner conductor Of a concentric line interrupted only by said sealed region, and a cylindrical conductive member concentrically surrounding said device and constituting an outer conductor for said concentric line, saidtransverse conductive member being conductively attached to said cylindrical conductive member, said cylindrical conductive member forming with said anode and cathode members at least portions of a pair of cavity resonators one on each side of said grid.

5. A high frequency cavity resonator apparatus comprising an electric discharge device including cylindrical anode and cathode members electron receiving surface and an electron emitting surface respectively, a transverse conductive member supporting a grid between said anode and cathode members in spaced relation to said ends, insulating means positioning said anode and said cathode members and said conductive member in an outer conductor for said second mentioned concentric line, said transverse conductive member being conductively attached to said cylindrical conductive members, said cylindrical conductive members forming with said anode and cathode members at least portions of a pair of cavity resonators one on each side of said grid.

'6; A high frequency cavity resonator apparatus comprising an electric discharge device including cylindrical anode and cathode members positioned in co-axial longitudinal alignment and having juxtaposed closed ends provided with an electron receiving surface and an electron emitting surface respectively, a transverse conductive member supporting a grid between said anode and cathode members in spaced relation to said ends, insulating cylinders of diameter equal to that of said anode and cathode members coaxially aligned therewith and positioning said anode and said cathode members and said conductive member in mutually spaced relation and forming a sealed region about said ends, said anode member constituting at least a portion of an inner conductor of a concentric line on one side of said grid, said cathode member constituting at least a portion of an inner conductor of a concentric line on the other side of said grid, a cylindrical conductive member concentrically surrounding said anode member and constituting an outer conductor for said first mentioned concentric line, and a cylindrical conductive member concentrically surrounding said cathode member and constituting an outer conductor for said second mentioned concentric line, said transverse conductive member being conductively attached to said cylindrical conductive members, said cylindrical conductive members forming with said anode and cathode members at least portions of a pair of cavity resonators one on each side of said grid.

'7. A high frequency apparatus comprising a pair of cylindrical cavity resonators each including concentric inner and outer conductors, said inner conductors being positioned in coaxial longitudinal alignment with each other and said outer conductors being positioned in coaxial longitudinal alignment with each other, an electron discharge device including a cylindrical anode member and a cylindrical cathode member having juxtaposed closed ends provided with an electron receiving surface and an electron emitting surface respectively and positioned in coaxial longitudinal alignment, a transverse conductive member supporting a grid between said anode and said cathode members in spaced relation to said ends, insulating means positioning said anode and cathode members and said transverse member in mutually spaced relation and forming a sealed region about said ends, said anode member having a diameter equal to that of one of said inner conductors and constituting a detachable extension thereof, said cathode member having a diameter equal to that of said other inner conductor and constituting a detachable extension thereof, said outer conductors comprising a cylindrical conductive member conductively connected to said transverse member, concentrically surrounding said discharge device and constituting with the said anode and cathode members at least a portion of said cavity resonators.

8. A high frequency apparatus comprising a pair of cylindrical cavity resonators each including concentric inner and outer conductors, said inner conductors being positioned in coaxial longitudinal alignment with each other and said outer conductors being positioned in coaxial longitudinal alignment with each other, an electron discharge device including a cylindrical anode member and a cylindrical cathode member having juxtaposed closed ends provided with an electron receiving surface and an electron emitting surface respectively and positioned in coaxial longitudinal alignment, a transverse conductive member supporting a grid between said anode and said cathode members in spaced relation to said ends, insulating cylinders of diameter equal to that of said anode and cathode members coaxially aligned therewith and positioning said anode and cathode members and said transverse member in mutually spaced relation and forming a sealed region about said ends, said anode member having a diameter equal to that of one of said inner conductors and constituting a detachable extension thereof, said cathode member-having a diameter equal to that of said other inner conductor and constituting a detachable extension thereof, said outer conductors comprising a cylindrical conductive member conductively connected to said transverse member, concentrically surrounding said discharge device and constituting with the said anode and cathode members at least a portion of said cavity resonators.

9. A high frequency apparatus comprising a pair of cylindrical cavity resonators each including concentric inner and outer conductors, said inner conductors being positioned in coaxial longitudinal alignment with each other and said outer conductors being positioned in coaxial longitudinal alignment with each other, an electron discharge device including a cylindrical anode member, and a cylindrical cathode member having juxtaposed closed ends provided with an electron receiving surface and an electron emitting surface respectively and positioned in coaxial longitudinal alignment, a transverse conductive member supporting a grid between said anode and said cathode members in spaced relation to said ends, insulating means positioning said anode and cathode members and said transverse member in mutually spaced relation and forming a sealed region about said ends, said anode member having a diameter equal to that of one of said inner conductors and constituting a detachable extension thereof, said cathode member having a diameter equal to that of said other inner conductor and constituting a detachable extension thereof, said outer conductors comprising cylindrical conductive members having abutting ends conductively connected to said transverse member, concentrically surrounding said discharge device and constituting with the said anode and cathode members at least a portion of said cavity resonators.

ELMER D. MCARTHUR.

(References on following page) Number Name Date REFERENCES CITED 2,169,396 Samuel Aug. 15, 1939 The following references are of record in the 2,263,184 Mouromtsefi et a1, Nov. 18, 1941 file of this patent: 2,284,405 McArthur May 26, 1942 5 2,289,846 Litton July 14, 1942 UNITED STATES PATENTS 2,353,742 McArthur July 18, 1944 Number Name Date 2,400,753 Haefi May 21, 1946 2,091,443 Heintz Aug. 31, 1937 2,128,236 Dallenbach Aug. 30, 1938 

